Hitherto, a copying machine as an image forming apparatus includes a printer section, an image reading section, and an auto document feeder to feed documents one by one to the image reading section. When a document is set on the auto document feeder, a document width detection sensor detects a document width as a length in a direction orthogonal to a document feed direction, and the document is sequentially read and is temporarily stored in a memory. The printer section includes one or plural paper feed cassettes to contain standard size sheets, and feeds a sheet in a selected paper feed cassette at a specified timing to an image forming section including, for example, a photoconductive drum and the like.
Besides, the copying machine includes a manual feed tray on which a user can arbitrarily stack a sheet irrespective of sheet size. When paper feed using the manual feed tray is selected, the sheet on the manual feed tray is fed to the image forming section. With respect to the sheets stacked on the paper feed cassette and the manual feed tray, the stack direction is determined on the assumption that the whole area of the document image of the same size is printed in equal magnification (first stack direction), or they are stacked in a direction (second stack direction) rotated by 90 degrees with respect to the first stack direction in order to perform reduced printing, enlarged printing or the like.
An image forming apparatus is proposed in which a manual feed tray is provided with a sheet width detection sensor to detect a sheet width as a length in a direction orthogonal to a conveyance direction of a stacked sheet, information of the sheet size is displayed on a display panel based on the sheet width of the sheet on the manual feed tray detected by the sheet width detection sensor, and the user selects the size of the sheet stacked on the manual feed tray from among plural sheet size candidates (JP-A-2006-018081).
For example, when the sheet width detection sensor detects a sheet width “a”, there is a case where the long side length of an A4 size sheet is detected as “a”, or the short side length of an A3 size sheet is detected as “a”. Besides, when the sheet width detection sensor detects a sheet width “b”, there is a case where the long side length of an A5 size sheet is detected as “b”, or the short side length of an A4 size sheet is detected as “b”. In such a case, selection is made as to the sheet size and as to whether the sheet stack direction is the first stack direction or the second stack direction.
As a result, in the related art image forming apparatus, duplex printing or printing with automatic variable magnification can be performed for the sheet stacked on the manual feed tray.
However, in the foregoing related art image forming apparatus, the use of the manual feed tray corresponds to only the standard image formation to print the whole area of the document image on the sheet in the same direction, and it can not be necessarily said that the function of the manual feed tray on which sheets of various sizes can be freely stacked is effectively used.